Hello,
All Guardian air cooled generators come with a fiberglass base that allows you to put it on any level ground. There is no need to pour a pad for these units.

In our installations, we level the area as best as possible, and put down (2) fifty pound bags of pea-stone. This pea-stone can be purchased from your local home depot or lowes. This provides a good site prep to properly level the generator.

If you decide to pour a cement pad, I would recommend making it 52"x28". The generator base itself is 48"x24". Pouring the pad 4" bigger will give a very nice look to the cement base around the generator.

I will include a photo of the base. (click on the small image for a bigger one)